The present invention relates to an exercise device, particularly but not exclusively to a dumbbell or barbell for weight lifting exercises and other fitness activities.
Conventional dumbbells or barbells comprise a bar and a set of weights mounted on the end portions of the bar. These dumbbells or barbells further comprise flanges and threaded securing means, such as a locking nut, to retain the weights in position on the bar and to secure the weights. The flanges are provided on the bar towards the end portions. The locking nuts are located on the end portions of the bar, over the weights, and are used to secure the weights on the bar by cooperating with the flanges to secure the weights therebetween.
These dumbbells or barbells have the problem that, through repeated use, the collars can become loose, thereby causing the weights to rotate, wobble and vibrate around the handle during use. This results in the dumbbell becoming awkward to use, and can eventually cause the weights to become disconnected from the bar, which can be extremely hazardous to the user.
Prior patent application GB2410197 seeks to address this problem by providing a dual fixing mechanism. The dumbbell of GB2410197 is provided with first and second securing members for securing the weight assembly to the end portion of the bar. The first securing member is a locking nut, which co-operates with a threaded portion on the bar, to force the weight against a flange section.
The second securing member comprises an end plate which engages with the weight. The end plate sits over the weight, and is held in place by means of a mounting screw, which engages with an internal thread in the end portion of the bar.
However, producing internal and external threads of a suitable quality for such an application, on a consistent basis, increases the cost of manufacturing a dumbbell. In addition, the high tensile screws which are required for the second fixing means also significantly add to the manufacturing cost, as well as being difficult to source. Furthermore, a thread locking compound, such as Loctite®, is required for dumbbells using threaded securing means, to prevent loosening, which again increases the cost per dumbbell.
The use of threaded securing means to retain the weight heads of a dumbbell in place also adds additional steps to the manufacturing process, which increases the manufacturing time and hence cost for each dumbbell. In addition to forming both the internal and external threads, the securing nut, and mounting screw must be attached and tightened, and the locking compound applied.
A poor tolerance between the end portion of a dumbbell bar and the inner bore of the weight head allows lateral movement of the bar within the inner bore, which eventually leads to wobbling and loosening of the securing means. However, for conventional dumbbells, the formation of a close tolerance bore between the weight head and the end portion of the bar is problematic. In particular, while the bar may be turned down to within relatively tight tolerances, it is difficult to achieve the same degree of accuracy when forming the bore within the weight head. This is mainly due to the low quality of the cast iron used to produce such weight heads at low cost.